1. Field of the Invention
The present invention relates to control of remote devices, and in particular, control of remotely located electrical equipment, including but not limited to, lighting systems.
2. Problems in the Art
Large area lighting systems are well known in the art. They can take many different forms. From baseball diamonds to playgrounds, to parking lots, to golf courses; large area lighting systems are all around in today's society.
In some instances, the lighting system is turned on and off automatically by timers, photo detectors, or other devices. This works reasonably well if the lights are used on a regular schedule or according to regularly repeating occurrences. In other cases, employees, staff members, or other persons must be hired or have the obligation to turn on and off the lights, particularly if the lights are used or needed only sporadically. Most of the time the person maintaining the lights will have to take care of several keys for several lights. These people usually travel back and forth between the field and his/her home and even field to field because the lighting is commonly used during non-business hours. In the time it takes a staff member to travel, the lights have been unnecessarily left on. Such a problem is further compounded when the staff member is not informed that the lights are no longer needed for a certain event. When the lights are not turned off, this results in a waste of energy. This waste usually results in a waste of taxpayer's money. The waste of taxpayer money is furthered by the presence of vandalism, which often occurs to remote lighting systems.
An ancillary problem with manual control of large area lighting systems is that the person in charge normally must handle keys for the electrical boxes or buildings in which the switches or breakers are located to turn the lights on and off. Access by the public at large to the switches is usually blocked for safety, economic, and practical reasons. Such keys must be carefully handled and be available to control the lights. This can be cumbersome.
There has been some work done with computerized control of electrical loads or systems. The computer can have a database of instructions that could include turning a device on or off. The computer could utilize its internal clock or other criteria to issue commands. However, such systems generally require a dedicated computer to control each device or no more than several devices at a location. Such systems also generally require special interactive software developed for each application. To change operation of the computer it must be reprogrammed, or new software must be installed. Either case requires significant time and expense.
Some attempts at remote control have been made. One example uses established paging systems as the carrier of instructions to remotely located devices which are to be controlled. Paging systems are attractive because they have currently developed to a point where they can carry a significant amount of digital data instructions. However, they can be somewhat costly, including communication costs.
The paging system could include a central repository of instructions. Control of remote devices based on the central repository is accomplished by sending out paging messages with control instructions carried therein to a paging receiver at the remote device. While this can eliminate many of the problems associated with other methods of operating lighting systems, a major deficiency with paging systems presently exists. In the United States, paging systems cover most densely populated geographic areas. Most major-sized cities have good coverage. However, coverage is lacking in many other places. Of course, electrical devices, including large area lighting systems, are not limited to big cities. In fact, the need for remote control of devices may be more urgent in less densely populated areas. Thus, while paging systems offer some promise, they simply will not work in some areas because paging communications do not reach those areas.
Furthermore, paging systems tend to be one-way only, and therefore of limited capacity and options. Two-way paging is presently only in development. Digital paging systems are also in development, but it is estimated that infrastructure for substantial geographic coverage is several decades away.
Remote control of devices using DTMF signaling is in use. An example is remote control of the functions of an answering machine by pressing different telephone keys. This can be accomplished over regular or cellular phones. However, because it involves establishing a telephone connection with the remote device, it must use the voice channels. This is not satisfactory. Voice channels are not always available. They can be unreliable. This also involves the cost of using the voice channel while communicating the instructions.
A wireless communications system with more geographical coverage is the cellular telephone system. It is attractive because of this broader geographic coverage and its existing infra-structure. Therefore, like the paging network, capital costs of developing and installing a new infrastructure could be avoided. It is also attractive because it has a built-in confirmation function. However, it is extremely limited in the data that it can carry, especially out to remote devices, without invoking its voice channels. For example, because of inherent limitation in the present cellular communications protocol in the USA (Advanced Mobile Phone Service or AMPS), it may be able to carry only three digits of instructions in each call via the last four digits on each cellular phone's Mobile Identification Number (MIN), a ten digit number in the form of a conventional telephone number; i.e. abc-def-wxyz, where a, b, c, d, e, f, w, x, y, and z are a single digit including and between 0 and 9, and where abc is the area code (three digits), def is the identification of the local central switching office (CTO) for the land based telephone system (three digits), and wxyz is a four digit identification for the phone (equivalent to the “line” number in conventional phone systems). This is well-known and widely documented.
Under Federal Communications Commission (FCC) regulations, two cellular phone carriers for each geographic area are each given 416 duplex voice channels, and 21 control channels. Carrier 1's channels are called the A channels and carrier 2's channels are called the B channels. Forward control channels (FOCC's) are from the cell base station to a cell phone; reverse control channels (RECC's) are from the phones to the base station. Under AMPS protocol, up to three digits in the MIN can be used for carrying data on the forward control channels.
An advantage of using the control channels of AMPS is that the messages are cheap because they are short and do not involve the voice channels. Also the control channels are transmitted at higher power than the voice channels, have better error correction and better frequency use, and have less traffic. Therefore, they are more reliable as a communication link.
Therefore, current cellular telephone systems and protocols (e.g. Advanced Mobile Phone System (AMPS) in North America; other similar analog systems are NAMPS and ENAMPS) are simply unacceptable because of the limitation of information that could be included as instructions or control in cellular calls.
To have meaningful control of remote devices usually requires communication of more than three digits of instructions. At a minimum, this limitation would not allow an acceptable of level of flexibility for many applications.
Also, the utilization of MINs to both serve to instigate a cellular call and, with the same number, effect an operation (e.g. turning lights on or off) at a remote site is not indicated as a realistic use of MINs or the cellular network.
One example of a cellular telephone based remote control system is that of Cellemetry of Atlanta, Ga. It provides the means of sending short, telemetry-like messages over the cellular telephone system. Examples include reporting (a) alarm panel status, (b) utility meter readings, (c) vehicle and trailer location, and (d) vending machine status. It does utilize the overhead control channels (FOCC's and RECC's) of cellular telephone systems to communicate the information. However, its primary uses involve transmitting data or information or status from remote locations to a central location.
One specific example involves soft drink vending machines. Reports can be communicated to a central location regarding how much product has been sold and/or how much money has been received and/or how much change has been dispensed. Another example involves turning off a machine or turning security on at the machine. However, there is no known ability with such systems to have individualized schedules or control options at each remote device that can be handled via the three digits of a cellular control channel registration message sent over the FOCC.
Such a system could use different MINs to set and reset flags in a programmable logic controller (PLC), for example, through a single input/output port, but there is no known controlling of resistive or inductive loads with MINs mapped in a PLC memory to functions. There is no known instruction set coded to MINs. The problem is one of availability of MINs. If each remotely positioned PLC with a cellular radio were given ten instructions to which it would respond, the cellular carrier would have to provide ten unique and distinct MINs for each such radio. If there were only two radios, only 20 MINs would be needed. But one hundred radios would need 1000 MINs. One thousand radios would need ten thousand MINs and so on. If there are any meaningful number of remote devices to be controlled (and remote radios), there would not be enough MINs or the number of MINs per phone would have to be restricted.
Essentially, cellular systems have wider coverage geographically than paging systems, but much more restricted data capacity. Therefore, cellular systems are not indicated to be viable candidates for flexible remote control of devices.
There is no known existing system that remotely controls resistive or inductive electrical loads according to a centralized schedule through the cellular system control channels.
The state of the art has not revealed a way of solving the conflicting concerns of cost, capacity, and coverage relative to centralized, automated control of multiple remotely located electrical devices. Therefore, there is a need for improvement in the art.